1. Field of the Invention
The present invention is directed to a system and to a method for generating an image dataset that contains superimposed or fused image data.
2. Description of the Prior Art
Various imaging modalities can be utilized for acquiring image data of an object, particularly from the inside of the object. The selection of the imaging modality ensues dependent on the subject to be examined or, if the object is a living subject, dependent on the tissue to be examined. It is especially advantageous when 3D image datasets of the subject to be examined or tissue to be examined can be acquired with the imaging modality. Diagnostically useful 3D images can be capable of being produced therefrom.
In medicine, x-ray computed tomography systems and magnetic resonance systems are usually employed for acquiring 3D image datasets of bone structures and of soft tissue. These 3D image datasets are of assistance in diagnostics since fractures as well as hemorrhages or other soft tissue injuries can be recognized. Moreover, 3D image datasets of bone structures can be acquired in conventional x-ray technology, for example with permanently installed or portable C-arm x-ray devices, and 3D image datasets of soft tissue can be acquired with ultrasound devices.
Nonetheless, it is disadvantageous that either only bone structures or only soft tissue can be recognized well as a rule in the images generated with the devices employing x-radiation or ultrasound.
German OS 40 21 102, however, discloses a medical diagnostic installation having two integrated, imaging systems, one being an x-ray system and the other being an ultrasound system. The surface or spatial allocation of an ultrasound tomogram generated with the ultrasound system to an x-ray image generated with the x-ray system is determined with the assistance of position sensors in order to be able to mix the ultrasound tomogram into the x-ray image. For this purpose, however, the x-ray system and the ultrasound system must be arranged in a defined way relative to one another in order to be able to produce a relationship between the image data of the x-ray system and of the ultrasound system.
The section xe2x80x9cBildrektifikationxe2x80x9d in xe2x80x9cLexikon der Computergrafik und Bildverarbeitungxe2x80x9d by Iwainsky, A. and Wilhelmi W., Vieweg Verlagsgesellschaft, 1994, pages 31, 32 describes methods for the geometrical and radiometrical correction of picture elements for the purpose of matching two images. Two methods for the geometrical correction are described, one being directed to the calculation of two-dimensional correction polynomials of the order k, and the other being directed to a perspective transformation method.
PCT Application WO 96/39939 discloses a method and a system for correlation of ultrasound image data with x-ray image data.
An object of the present invention is to provide a system and a method for generating images of a subject which allow the images to be generated in a simple way, the images containing information acquired with two imaging modalities that are different from one another.
According to the invention, this object is achieved in a system for generating an image dataset that contains superimposed or fused image data, having a first image acquisition system for acquiring a first image dataset of a subject, a second system different from the first for acquiring a second image dataset of the subject, a navigation system for determining the positions of the first and the second systems in the acquisition of the image datasets, a unit for determining the position of the first image dataset acquired with the first system and the position of the second image dataset acquired with the second system, and a unit for superimposition and fusion of the image data of the first image dataset and the second image dataset. Inventively, the positions or the attitudes of the image datasets in space generated with the first and second systems can be determined with a computational unit, for example with a computer, from the identified positions that the first and the second systems assumed in the acquisition of the first and second image dataset. The knowledge of the attitudes of the image datasets acquired with the first and second systems, finally, allows these to be superimposed on one another or allows these to be fused with one another to form an image dataset. Finally, images that contain information that were acquired with two different imaging modalities are acquired from the image dataset comprising superimposed or fused image data. A navigation system is provided for determining the positions of the first and the second systems in the acquisition of the image datasets. The navigation system has contact-free sensors for determining the position of a subject in space. For example, the navigation system can be a known optical navigation system, an electromagnetic navigation system, a navigation system operating with acoustic waves, for example ultrasound, or some other known navigation system.
In one embodiment of the invention, the attitudes and position of the subject also can be identified in space with the navigation system. The determination of the attitudes and positions of the subject during the acquisition of the image datasets maybe required under certain circumstances when the subject to be examined is not inmmovably fixed during the acquisition of the image datasets, or when the acquisition of the two image datasets does not ensue simultaneously and the subject moves or is moved between the acquisition of the two image datasets. Accordingly, the subject is in a different attitude in the image dataset acquired with the first system than in the image dataset acquired with the second system. The two image datasets therefore cannot be superimposed on one another without further difficulty or fused with one another. Due to the acquisition of the movement of the subject, it is ultimately possible to adapt the two acquired image datasets to one another taking the movements of the subject into consideration such that a superimposition or fusion of the two datasets can ensue.
In a preferred embodiment of the invention, 3D image datasets can be acquired with the first system and/or with the second system for acquiring the respective image dataset. The first system can be an x-ray system, preferably a C-arm x-ray system, and the second system can be an ultrasound system. In this way, image datasets of life forms can be produced from which images can be reconstructed wherein bone structures as well as soft tissue are presented. The advantage of employing a C-arm x-ray system and an ultrasound system for generating the two image datasets to be superimposed on one another, or the two image datasets to be fused with one another, lies in the relatively economic production of the image datasets compared to the acquisition of datasets with an x-ray computer tomography apparatus or a magnetic resonance apparatus. Moreover, the examination subject need not be repositioned in the acquisition of the image datasets with a C-arm x-ray system and an ultrasound system, as is usually the case given acquisition of the image datasets with an x-ray computed tomography apparatus and a magnetic resonance apparatus.
The above object also is achieved in a method for generating an image dataset that contains superimposed or fused image data having the following method steps:
a) Acquisition of a first image dataset of a subject with a first system for acquiring image data;
b) Acquisition of a second image dataset of the subject with a second system for acquiring image data different from the first system;
c) Determining the positions of the first and the second systems in the acquisition of the image datasets with the navigation system
d) Determining the position of the first image dataset acquired with the first system and the position of the second image dataset acquired with the second system; and
e) Superimposition or fusion of the image data of the first image dataset and the second image dataset.
The positions of the first and second systems in the acquisition of the image datasets can be determined in a simple way with the navigation system. Proceeding from the identified positions of the first and second systems, the positions of the image datasets acquired with the first and second systems also can be identified, so that these can be superimposed on one another or fused with one another in a simple way.